Structural studies of the human erythrocyte membrane sialoglycoprotein(s) will continue; we hope to resolve the basis for its heterogeneity and resume investigation of the primary structure of its polypeptide and carbohydrate chains. The protein will be used as a tool to probe the arrangement of other proteins and lipids in its vicinity: after chemical modification by mild periodate treatment in situ the protein will serve as a polyfunctional crosslinking agent. In addition, we will use this protein as a model for studies of surfaces and functional properties of other cells, in particular the diploid human lung fibroblast WI38 in culture and the human lymphocyte. Chemical modification including mild periodate or galactose oxidase treatment followed by reduction with tritiated sodium borohydride or stabilization with CN14 will be used to develop methodology for studies of cell surface glycoproteins and glycolipids. Classical Kiliani-Fisher synthesis reactions will be adapted to modify residues in glycolipids. Investigation of interaction of serum and cell membrane lipoproteins (cholesterol) will continue with purpose of developing experimental approaches, and an understanding of the role of serum lipoproteins in the modulation of membrane structure and function. Such interaction with serum glycolipids will be initiated, focusing on functional consequences.